In the past, there have been used rotary compressors in which a cylinder including a cylinder chamber and a piston accommodated in the cylinder chamber move relative to each other, thereby compressing a refrigerant. In a rotary compressor, the cylinder chamber is sectionalized into two compression chambers, and the refrigerant is compressed by the cyclic increasing and decreasing of the volumes of the compression chambers.
A compressor including a piston having a blade is disclosed as an example of a rotary compressor in Japanese Laid-open Patent Publication No. 2004-29358. The blade, which is formed integrally with the piston, sectionalizes the cylinder chamber into two compression chambers. The blade is sandwiched between a pair of bushings provided in a bushing hole of the cylinder, each bushing having a substantially semicircular cross section. The blade Moves back and forth between the pair of bushings, whereby the bushings oscillate within the bushing hole while sliding against the cylinder and the blade.
In this compressor, because the cylinder and the piston move relative to each other with the bushings therebetween, the portion where the cylinder and bushings slide against each other and the portion where the piston and bushings slide against each other must exhibit exceptional sliding and wear-resistance properties. In the past, iron-based materials have mainly been used as the materials of the cylinders and pistons constituting the sliding portions, but the use of aluminum-based materials has recently been investigated. The cylinder and the piston must be precisely machined in order to make the gap between the bushings as small as possible. With an iron-based material, cutting and a polishing process are needed in order to perform high-precision machining. With an aluminum-based material, cutting alone is sufficient for high-precision machining, and machining costs can be decreased. Furthermore, the weight of the cylinder and the piston can be reduced by changing from an iron-based material to an aluminum-based material.